Induction of specific cytotoxic lymphocytes in mice vaccinated with Brucella abortus RB51

A safe, more sensitive, nonradioactive, neutral red uptake assay was adopte d to replace the traditional Cr-51 release assay for detection of Brucella- specific cytotoxic T lymphocyte (CTL) activity. Our studies indicated that Brucella abortus strain RB51 vaccination of mice induced specific CTLs agai nst both strain RB51- and strain 2308-infected J774.A1 macrophages but not against Listeria monocytogenes-infected J774.A1 cells. The antigen-specific cytotoxic activity was exerted by T lymphocytes but not by NK cells. CD3() CD4(+) T cells secreted the highest level of gamma interferon (IFN-gamma) and were able to exert a low but significant level of specific lysis of Br ucella-infected macrophages. They also exerted a low level of nonspecific l ysis of noninfected macrophages. In contrast, CD3(+) CD8(+) T cells secrete d low levels of IFN-gamma but demonstrated high levels of specific lysis of Brucella-infected macrophages with no nonspecific lysis. These findings in dicate that B. abortus strain RB51 vaccination of mice induces specific CTL s and suggest that CD3(+) CD4(+) and CD3(+) CD8(+) T cells play a synergist ic role in the anti-Brucella activity.